fast即可作形容词也可作副词,都用来描述具有物理性质的、量化的“速度、速率”的快慢,如：
Tom runs faster than Peter.
4m/s is faster than 2m/s.
而quickly只用作副词,多用来形容无量化的快慢,如：
Quickly Tom!Come here!(which means:Tom!Come here quickly!)
Do it quickly,or we'll be knocked out!
fast即可作形容词也可作副词,都用来描述具有物理性质的、量化的“速度、速率”的快慢,如：
Tom runs faster than Peter.
4m/s is faster than 2m/s.
而quickly只用作副词,多用来形容无量化的快慢,如：
Quickly Tom!Come here!(which means:Tom!Come here quickly!)
Do it quickly,or we'll be knocked out!